I thought it would be nice for you guys to play around with this, I have got my answer, lets see if anyone views it the same way. There is a gene coding for a protein. The protein can either have amino acid A on the end or the aminoacid B. It turns out that humans only have amino acid B, since we have a deletion in the gene. Chimpansees have amino acid A though, so the deletion took place after we diverged from the chimp. Now, scientists isolated proteins from Neanderthaler bone and found that also here, only form B is present. So the deletion predates our common ancestor, about 2.7 Mya (million year ago). Is it thinkable that a founder effect has caused humans to loose from A of the gene, and how would you test that hypothesis?